Sexual and gender minority (SGM) patients may experience poor quality of healthcare due to stigma and discrimination. This qualitative study explored diagnostic challenges and the impact of diagnostic errors among 20 participants identifying as sexual minorities and/or gender minorities. Participants attribute diagnostic error to provider-level and personal challenges and how diagnostic error worsened health outcomes and led to disengagement from healthcare. The authors of this article also summarize patient-proposed solutions to diagnostic error through the use of inclusive language, increasing education and training on SGM topics, and inclusion of more SGM individuals in healthcare.